1. Field of the Invention
This invention relates generally to appliance transparencies, such as but not limited to, windows for conventional ovens, microwave ovens, convection-microwave ovens, self-cleaning ovens, refrigerators, furnaces and the like, through which material inside the appliance can be viewed.
2. Technical Considerations
Appliances, such as conventional ovens, microwave ovens, convection-microwave ovens, self-cleaning ovens, refrigerators, and furnaces, just to name a few, often have a transparency through which material inside the appliance can be viewed. These appliance transparencies have sufficient visible light transmittance such that material inside the appliance can be viewed but also have heat or radiation reflecting elements to reduce heat or radiation passing through the transparency.
For example, some conventional oven doors have a transparency formed by two or more spaced glass sheets. The sheets have heat reflective coatings on both their inner and outer surfaces to reduce heat from the interior of the oven escaping into the ambient atmosphere. One widely used heat reflective coating for this purpose is a fluorine-doped tin oxide coating. This fluorine-doped tin oxide coating is typically applied to the glass sheets by spray pyrolysis. While adequate for heat reflection, this conventional appliance transparency structure does have some drawbacks. For example, spray pyrolysis of the fluorine-doped tin oxide coatings can result in uneven coating thickness across the surface of the sheet. This uneven coating thickness can lead to color and reflectance variations in the coated sheet that can be aesthetically undesirable. Additionally, this conventional oven transparency structure requires the application of four separate coatings (one coating on each side of the two sheets). Moreover, this construction requires multiple glass sheets.
Conventional microwave oven doors are typically formed by an inner polymeric panel, such as a Mylar sheet, an intermediate wire mesh grid or screen, and an outer glass sheet. The inner Mylar panel provides ease of cleaning and the intermediate wire mesh screen prevents microwave radiation from the interior of the oven passing through the transparency. Again, while adequate for its intended purposes, this conventional microwave oven door structure does have some drawbacks. For example, the conventional microwave oven door requires three separate pieces that must be assembled in order for the door to function properly. Moreover, it may be difficult to adequately view material inside the oven through the wire mesh screen.
Therefore, it would be advantageous to provide a coated sheet or panel that can be utilized in appliance transparencies that reduces or eliminates at least some of the drawbacks described above. For example, it would be advantageous to provide a conventional oven door in which fewer than four coatings were needed to provide acceptable performance. Additionally, it would be advantageous to provide a microwave oven transparency that eliminates at least some of the required components of conventional microwave oven transparencies and/or provides increased visibility through the microwave oven transparency.